Lifting clamp



Oct. 30, 1951 s. ROBSON LIFTING CLAMP liled Dec. 1. 1949 IIVVENTOR Stan Ze Ro6$0fg Patented Oct. 30, 1951 LIFTING CLAMP Stanley Robson, Parktown, Johannesburg, Transvaal, Union of South Africa Application December 1, 1949, Serial No. 130,405 In the Union of South Africa November 24, 1949 1 Claim. (01. 294-106) This invention relates to lifting clamps to enable plates of steel or other materials to be lifted.

The object of the invention is to provide an automatically operated lifting clamp which, under load, will retain its grip at any angular position between the horizontal and the vertical.

According to this invention there is provided a lifting clamp comprising a pair of internally cam surfaced clamping jaws, pivots for the lower parts of the jaws connected by an inwardly arched bridging member, and a pair of pantographic links rotatably connected together at their upper ends and each pivotally connected at their lower end to the upper part of each corresponding jaw. Stops are provided limiting the outward movement of the jaws.

The invention is illustrated in one preferred form in the accompanying drawings in which:

Fig. I is a side elevation of the clamp;

Fig. II is a similar viewto Fig. I showing the clamp in its horizontal lifting position;

Fig. III is a side elevation of the clamp in its vertical lifting position; and

Fig. IV is a side elevational view, showing the clamp in the position illustrated in Fig. III.

As shown in the drawings there is provided a pair of clamping jaws I, 2, which are pivoted near their ends 3, Al on pins 5, 6. The jaws I, 2 are internally cam shaped, that is, they are made to protrude towards one another. The pins 5, 6 are connected by means of an arched shaped bridging member which conveniently takes the form of the frame I. The frame'l consists of a pair of opposite plates 8 rigidly held parallel to each other by the ties 9. The bottoms III of the plates 8 have inwardly extending gaps or recesses II to enable a plate to be inserted between the jaws I, 2.

The jaws I, 2, are positioned between the parallel plates 8 and and are provided with suitably hardened and serrated clamping faces I2, I3 of cam shape,

Pins I4, I are fitted through the upper portions I6, II of the jaws I, 2 and project through arcuate slots I8, I9 in the plates 8, which act as stops to limit the movement of the pins I4, I5 and thus the jaws I, 2.

On the outer ends of the pins I4, I5 are r0- tatably fitted a pair of pantographic links 20, 2| which in turn are connected at their upper ends by pin 22. Pin 22 carries a U shaped lifting shackle 23 into which the hook 24 of a crane or other lifting device may be passed.

For use the frame 8 is positioned on its side and the edge of the plate 25 to be lifted is inserted between the jaws I, 2 as shown in Fig. I. In this position the pin I4 rests on the outer end of slot I8 and plate 25 rests on the face [2 of jaw .to lift the load the pins It,

I which latter projects a small amount across recess II and the face I 3 of jaw 2 rests on plate 25. As the shackle 23 and links 2s, 2l are raised I5 swing inwardly until pin I5 bears against the end of slot I9 thus limiting any further inward movement of jaw 2 relative to frame 8 as shown in Fig. II. In this position the inward movement of pin is is limited by jaw I bearing against the bottom of plate 25 which is thus gripped between jaws I and 2. If the plate 25 is gripped by two or more clamps at opposite edges this will be the normal position of the lifting clamps.

If, however, the plate 25 is lifted by a single clamp, as said plate is swung from the horizontal to the vertical position, the jaws I, 2 will swing from the positions shown in Figs. I or II to centralise themselves across the recess It as shown in Fig. III. It will be seen that the pantographic action of links 29, El and jaws I, 2 will cause the faces I2, I3 of the latter to grip the plate 25 in all positions between the horizontal and vertical.

The clamping action will be increased as plate 25 approaches the vertical position. This is due to the position of pins 5, 5 relative to the clamping faces I2, I3 which result in the latter having a wedge-like action as the downward pull of the weight of plate 25 becomes effective.

This invention thus provides a lifting clamp of simple construction which acts efficiently to grip a plate, or the like, in all normal positions.

What I claim as new and desire to secure by Letters Patent is:

A lifting clamp consisting of a pair of plates rigidly held in parallel spaced relation, corresponding centrally positioned inwardly arched recesses, one in the bottom of each plate, a pair of clamping jaws, serrated cam shaped clamp ing faces for the jaws projecting across said recesses, a pair of pivots in the clamp one positioned on each side of the recess for holding the outer ends of the jaws, a pair of arcuate slots in each plate, pins fitting through the upper portions of the jaws and projecting through said arcuate slots, a pair of pantographic links rctatably connected at their inner ends to the pins and a shackle rotatably connected to the outer ends of said links.

' STANLEY ROBSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,024,222 Hinchman Dec. 17, 1935 2,366,151 Stahl Jan. 2, 1945- 

